The present invention generally relates to video signal recording and reproducing apparatuses, and more particularly to a video signal recording and reproducing apparatus which records at the time of a recording a sampled signal which is obtained by sampling an input composite video signal at a frequency slightly higher than an upper limit frequency of a frequency band required by the input composite video signal, and obtains a reproduced video signal at the time of a reproduction by alternately and time-sequentially multiplexing for every one sampling point two kinds of reproduced sampled signals having a mutual time difference of one field.
Generally, a helical scan type video tape recorder (hereinafter simply referred to as a VTR) records at the time of a recording a video signal on a traveling magnetic tape by use of one or a plurality of rotary heads, and reproduces at the time of a reproduction the recorded video signal from the magnetic tape by use of the one or plurality of rotary heads. The above video signal has a wide frequency band having an upper limit frequency of 4.2 MHz, for example. For example, in order to frequency-modulate the video signal having the wide frequency band and record and reproduce the frequency modulated video signal on and from the magnetic tape, it is necessary to set a relative speed between the head and the magnetic tape to a high speed over a predetermined value and use a high-performance head which is highly sensitive in the high-frequency range, as is well known.
However, in the case of a VTR for home use, the relative speed between the head and the mangetic tape is inevitably set to a speed which is considerably smaller than the predetermined value due to the necessity to reduce the size and weight and manufacture the VTR for home use at a low cost. For this reason, the recording and reproducing frquency band of the VTR for home use became narrower than the original frequency band of the video signal, and this interfered with the reproduction of a picture having a high picture quality.
Accordingly, one of the inventors of the present application has previously proposed a video signal recording and reproducing apparatus in a U.S. patent application Ser. No. 620,016 entitled "VIDEO SIGNAL RECORDING AND REPRODUCING APPARATUS" filed June 13, 1984. According to this previously proposed video signal recording and reproducing apparatus, a recording video signal is sampled at a frequency f.sub.s which is slightly higher than the frequency band of the recording video signal, and the sampled signal is recorded on a recording medium. The signal which is reproduced from the recording medium is delayed by one horizontal scanning period, and the delayed signal and an undelayed signal are alternately sampled at the frequency f.sub.s and mixed so as to obtain a reproduced video signal which has essentially been sampled at a frequency 2f.sub.s which is twice the frequency f.sub.s. According to this previously proposed apparatus, it is possible to reproduce signal components in a relatively high frequency range, with a relatively narrow frequency band, and thus, it is possible to obtain a reproduced video signal having a wide frequency band.
However, according to the previously proposed apparatus, the sampling frequency f.sub.s is selected to an odd number multiple of the horizontal scanning frequency f.sub.H of the video signal, that is, f.sub.s =(2n+1)f.sub.H /2, where n is an integer. On the other hand, since the video signal can be divided roughly into the system employing 525 scanning lines and the system employing 625 scanning lines, the sampling point within the picture varies for every one frame (two fields). For this reason, when the video signal has no vertical correlation, such as the case where the video signal is related to an oblique line in the picture, a phenomenon which is sometimes referred to as a crawling phenomenon occurs. When this crawling phenomenon occurs, there is a problem in that the oblique line which should actually be stationary in the picture, drifts upwardly or downwardly in the picture. Moreover, because the previously proposed apparatus employs a 1H delay circuit for producing a time delay of one horizontal scanning period, there is also a problem in that the resolution in the vertical direction of the picture becomes deteriorated. In the present specification, the resolution in the vertical direction of the picture will simply be referred to as the vertical resolution.
Further, at the time of the recording, the previously proposed apparatus also performs the sampling with respect to the synchronizing signals of the input composite video signal. Hence, when a jitter is introduced between timing of the edge of the synchronizing signals and the timing of the sampling pulse having the sampling frequency f.sub.s, there is a problem in that the sampled composite video signal which is recorded will include the jitter. In addition, at the time of the reproduction, the re-sampling is performed at all signal intervals, that is, even in the intervals other than the video interval of the video signal. As a result, there are problems in that the circuit construction cannot be simplified and the circuit cannot be manufactured at a low cost.